1. Field of the Invention
The present invention relates to a semiconductor structure and a method of fabricating the same, and more particularly to a semiconductor structure including a composite pad structure and a bump and a method of fabricating the same.
2. Description of Related Art
In the flip chip package technology, a plurality of bonding pads is disposed on the active surface of the chip and bumps are formed on the bonding pads respectively. Thus, the chip is electrically connected to the carrier via the bumps on the bonding pads and then to the external electronic devices through the inner circuit of the carrier. Herein, the bonding pads are aluminum bonding pads, and the bumps are gold bumps formed by the wire-bonding process. Generally, in order to form the bumps in a place away form the bonding pads, an insulating layer with an opening exposing the bonding pads can firstly be formed on the chip after the plurality of bonding pads has been formed on the chip, and a conductive layer that is electrically connected to the bonding pads, the passivation layer with an opening exposing the conductive layer, and the bumps filling the opening are formed on the insulating layer sequentially, such that the bumps are electrically connected to the bonding pads via the conductive layer. To give an example, an entire layer of aluminum metal layer is formed between the aluminum bonding pads and the gold bumps, so that the gold bumps are electrically connected to the aluminum bonding pads via the aluminum metal layer.
However, when the gold bumps are electrically connected to the aluminum bonding pads via the aluminum metal layer, the gold of the gold bumps easily diffuses to the aluminum metal layer beneath and reacts therewith under high temperature and high pressure when operating the chip. Therefore, the gold-aluminum intermetallic compound is formed and defects such as a slit and the like are generated at the interface of the gold bumps and the aluminum metal layer. The slit deteriorates the adhesion between the aluminum metal layer and the insulating layer on the chip and the adhesion between the aluminum metal layer and the aluminum bonding pads, thereby influencing the electrical connection between the gold bumps and the aluminum bonding pads. Hence, the lifetime and the reliability of the semiconductor device are affected greatly.